Spring action expansion bolt

ABSTRACT

A masonry expansion bolt employs one or more resilient wires as the expansible wedging member which is positioned in annular grooves along the external surface portion of the bolt shank, the wedging member being selectively expansible in an outward radial direction into wedging engagement with the wall of the hole in which the bolt is inserted to firmly anchor the bolt in place in a positive and reliable manner.

The present invention relates to novel and improved fasteners, and moreparticularly relates to a spring action, wedge-type masonry expansionbolt of the type in which one or more resilient wires define a wedgingmember which will undergo outward radial expansion into firm anchoredengagement with the wall of a bolt hole.

Numerous types of expansion bolts have been devised for anchoringstructural members in masonry or rock materials and the like.Representative of this type of bolt are the various forms of masonryexpansion bolts disclosed in U.S. Pat. No. 3,257,891 to Lester Lerichentitled WEDGE-TYPE EXPANSION BOLT and wherein wedging members looselyassembled in external recesses on the shank of the bolt are normallypositioned to lie substantially within the preipheral surface of thebolt as the bolt is inserted into the bolt hole; and when the bolt istightened within the hole, the wedging members will automatically slideoutwardly along the external recesses into firm anchored engagement withthe wall of the hole. While these and other bolts of the type describedhave been found to be highly effective in commercial use and practice,there are applications where it is desirable to provide for a masonryexpansion bolt which will permit utilization of simplified forming andassembly operations with low-cost parts and specifically with a low costwedging member in the form of a resilient wire which is automaticallydisplaceable into uniform wedging engagement within the bolt hole.

It is therefore an object of this invention to provide for a novel andimproved wedge-type expansion bolt specifically adapted for use inanchoring members in masonry or rock materials.

Another object of the present invention is to provide for a novel andimproved masonry anchor having a spring wire wedging member sopositioned and arranged as to be rapidly and automatically displaceableinto uniform wedging engagement with the wall of an opening either asthe bolt is inserted into the hole or as the bolt is tightened in thedirection of withdrawal from the hole.

A further object of the present invention is to provide for a novel andimproved masonry anchor provided with spring action wedgeing elementswhich are responsive to rotation of the bolt within the hole to beautomatically displaceable into anchored engagement with the hole.

It is a still further object of the present invention to provide for anovel and improved masonry anchor bolt in which one or more resilientwire elements are so positioned and arranged on the external surface ofthe bolt shank as to be automatically and selectively expansible intowedging engagement with the wall of the hole when the shank is urged inthe direction of withdrawal from the hole.

It is a still further object of the present invenntion to provide in amasonry anchor bolt for a novel and improved spring action wedge memberwhich is automatically displaceable in an outward radial direction andin such a way as to effect full circumferential wedging engagement withthe wall of the hole at uniformly spaced intervals along at least aportion of the length of the bolt.

In accordance with the present invention there has been devised animproved form of spring-action expansion bolt in which a bolt of a givensize or diameter can be anchored in different sized openings withinlimits, the expansion bolt being of simple and inexpensive constructionand including improved wedging means preferably in the form of aresilient wire disposed in the annular grooves separating the threadsalong a threaded section of the bolt. The resilient wire wedging meansmay either be in the form of one or more split annular rings or in theform of a spiral coil preferably having a number of turns less than thenumber of threads on the bolt; and in either case the wire means is sodimensioned that when positioned within the annular grooves separatingthe threading on the bolt will be resiliently urged outwardly under itsspring tension into contact with the wall of the hole. In certain formsof the invention to be hereinafter described, as the bolt is insertedinto the hole, the resilient wire wedging means will be urged into thedeeper portion of the groove; and, when the bolt is then drawn or pulledoutwardly in the direction of withdrawal from the hole, the contactbetween the wedging means and the wall of the hole will cause thewedging means to slide forwardly along divergent bearing surfaces intofirm anchored engagement with the wall of the hole to firmly anchor thebolt in place. In another form of invention, the threading on the boltis tapered forwardly toward the leading end of the bolt and theresilient wire urging means will be caused to travel or rotaterearwardly away from the leading end of the bolt so as to undergoincreasing expansion as a result of the progressively increased diameterof the threading until it is anchored firmly in engagement with the wallof the hole.

In still another version of the present invention, the resilientwire-wedging means is so positioned and arranged with respect to thethreaded portion on the expansion bolt that it will be caused to undergocircumferential expansion or unwinding as the bolt is threaded orrotated in a direction opposing the spiral direction of the wedgingmeans. For example, if the resilient wire has a right-hand helix and isanchored at its trailing end, rotation of the bolt in a clockwisedirection will cause the righthand spiral wire to be expanded outwardlyas it engages the wall of the hole when the bolt is threaded or rotatedinto the hole.

In still another form of expansion bolt, in accordance with the presentinvention, the wedging means is defined by a resilient wire having apolygonal cross-section so that the wire can be normally disposedagainst a flat surface in the deeper portion of the annular grooveseparating the threading and can be selectively tipped into a shallownotch in the deeper portion of the groove causing its diagonal dimensionwhich is of greater thickness to project outwardly in a radial directionfrom the groove into firm wedging engagement with the wall of the holeas the bolt is threaded or screwed into the opening. Accordingly, itwill be appreciated from the foregoing and from the detailed descriptionof preferred and modified forms of invention which follow that thespecific configuration of the threading and associated grooves as wellas that of the wire may be modified to some extent to accomplishdifferent desired objectives dependent upon the intended application ofeach form of bolt. While each form contains separate and distinctpatentable features it will be further recognized that all arecharacterized by ease of assembly of the wedging means onto a bolthaving either standard or special threading to accommodate the wedgingmeans, and the resiliency of the wedging means is such as to permitrapid automatic displacement into firm engagement with the wall of thehole. At the same time, the resilient wire wedging means is capable ofeffecting not only uniform circumferential wedging engagement with thewall of the hole but of effecting such engagement at axially spacedintervals or continously in a spiral direction along a substantiallength of the hole.

The above and other objects, advantages and features of the presentinvention will become more readily understood and appreciated from aconsideration of the following description of the preferred andalternate forms of the present invention when taken together with theaccompanying drawings, in which:

FIG. 1 is an elevational view partially in section illustratinginstallation of a preferred form of expansion bolt, in accordance withthe present invention, in a drilled hole formed in a masonry wall.

FIG. 2 is a view similar to FIG. 1 showing the preferred form ofinvention in anchored relation within the hole.

FIG. 3 is an elevational view illustrating installation of an alternateform of the present invention in a drilled hole.

FIG. 4 is an elevational view of the form of invention shown in FIG. 3in anchored relation to the hole.

FIG. 5 is an elevational view of a modified form of invention andfurther illustrating in dotted form outward expansion of the wedgingmeans as the bolt is threaded into a drilled hole.

FIG. 6 is an elevational view of still another modified form partiallyin section prior to installation in a drilled hole; and

FIG. 7 is a detailed sectional view illustrating the particular mannerof expansion of the wedging means shown in FIG. 6 into anchored relationto the wall of a hole.

Referring in more detail to the drawings, one preferred form ofexpansion bolt 10 is illustrated in FIGS. 1 and 2 and is seen tocomprise an elongated cylindrical shank 12 having a threaded end portion13 at its external or trailing end and a wedging assembly generallydesignated at 14 extends for approximately one-half the total length ofthe bolt along the forward portion of the bolt and terminates at theleading end portion 15. The bolt assembly is completed by a washer 11and nut 9 which are employed to tighten the bolt in the hole byautomatic displacement of the wedging assembly into anchored engagementwith the surrounding wall surface W of the drilled hole H.

In the form of invention shown in FIGS. 1 and 2, the wedging assembly 14consists of ridge portions defined by axially spaced, forwardlydivergent surface projections 18 separated by annular grooves 19throughout the length of the wedging assembly. Although not essential,the projections 18 extend circumferentially for a full 360° around theexternal surface of the shank, and the distance or spacing betweenridges or projections 18 is uniform along the length of the assembly.Each ridge is generally V-shaped in cross-section and terminated in anouter pointed or sharply tapered circumferential extremity 20 which isof a diameter equal to that of the greater diameter of the shank 12.

Each of the annular grooves 19 includes a deeper surface portion 22which diverges forwardly at a low gradual angle from a stepped orshoulder portion 23 on one side of a ridge 18 and a second bearingsurface 24 which diverges forwardly at a steeper angle and forms theopposite side of each ridge 18 to that of the shoulder surface 23. Inaddition, the trailing groove of grooves 19 terminates in a steppedsurface 23' which merges into the main body of the shank portion 12.

The wedging assembly is completed by a plurality of wedging means 26each in the form of an annular ring of circular cross-section which isdisposed in one of the annular grooves 19 behind the ridge portion 18.Each of the annular rings includes split end portions 28 and a flattenedsurface portion 30 diametrically opposite to the split end portions 28.Most desirably, the cross-sectional diameter of each ring 26 correspondsto the depth of the annular groove at its deepest point which in thiscase is directly adjacent to the stepped surface or shoulder portion 23.In addition, each ring is given some limited resiliency so that when itis placed on the bolt by expanding at the split end portions and passedover the surface of the bolt it will be sprung outwardly away fromsnug-fitting engagement with the surface of the groove to a limitedextent. The flattened surface portion 30 diametrically opposite thesplit end portion 28 of the ring will permit ease of flexing at thatpoint in expanding the ring and returning it to a retracted position butagain spaced somewhat outwardly of the deeper surface portion of thegroove so that its effective circumference or diameter on the bolt willbe slightly greater than the diameter of the bolt itself. As a result,when the bolt is inserted into the hole, each ring will be forcedrearwardly into the deeper portion of the groove and sprung inwardly bythe force applied by the wall of the hole so as not to interfere withfull insertion of the bolt to the desired depth of the drilled hole.However, when the bolt is tightened by threading the nut 9 forwardlyalong the threaded portion 13 of the bolt, the resiliency of the ringsis such that they will be automatically displaced by frictionalengagement with the hole forwardly along the deeper bearing surface 22so as to be expanded outwardly into firm positive engagement with thewall of the hole. Depending on the exact size or diameter of the hole,the rings 26 may undergo continued expansion as they are forcedoutwardly along the bearing surfaces 24. Accordingly, the annular ringswill effect substantially complete circumferential engagement with thewall of the hole at spaced intervals from the leading end of the boltover the greater length of the inserted portion of the bolt in a hole.

In an alternate form of expansion bolt shown in FIGS. 3 and 4 the boltmember 35 is in the form of a screw anchor having a shank portion 36, aheaded external end 38 and externally threaded section 40 which extendsthe greater length of the shank portion of the bolt. The threadedsection 40 forms a part of the wedge assembly of this modified form ofbolt and has helical threads thereon. The threaded portions 42 aregenerally V-shaped in cross-section to define corresponding V-shapedannular grooves 44 therebetween, each annular groove having a forwardlydivergent bearing surface 45 and rearwardly divergent bearing surface 46defining opposite sides of each threaded portion 42. In addition, thethreaded section 40 tapers forwardly from the shank portion 36 towardthe leading end 46; or in other words, the threading is of progressivelyincreasing diameter from the leading end 46 to a maximum diametercorresponding to the diameter of the shank portion 36.

In the modified form shown in FIGS. 3 and 4, the wedging means takes theform of a coiled or a spiral spring wire 48 made up of a number of turnsless than the threaded portions and where the cross-sectional size ofthe wire is such that it will fit within the annular groove 44 with theexternal surface of the wire 48 projecting slightly beyond the outerperiphery of the threaded portions when positioned along the section oflesser diameter at the leading end so as to assure initial frictionalengagement with the wall of the hole. Thus, when the screw anchor isinserted into a drilled hole H and is caused to undergo inward threadingor rotation, the wedging means 48 which is initially positioned at theleading end of the threaded section 40 would travel in a rearwarddirection along the annular grooves 44 away from the leading end as aresult of a frictional contact with the wall of the hole and, due to theincreasing diameter of the threaded portion rearwardly toward the shank,the spring wedging means will be caused to undergo gradual expansion, asillustrated in FIG. 4, until it effects positive anchored engagementwith the wall of the hole. In addition, the wedging means will exertsomewhat greater pressure against the forwardly divergent bearingsurfaces 45 to assure positive anchored engagement with the wall of thehole, since the anchor when tightened in the hole will be under tensionwhich will apply force in the direction of withdrawal from the holecausing the wedging means to bear more firmly against the bearingsurfaces 45. Of course the threading may be either righthand or lefthandand the screw anchor must be threaded or rotated into the hole in adirection which will cause the wedging means to travel in the oppositedirection by frictional engagement with the wall of the hole. Where theturns of wire are as in this form substantially less than the number ofthreads on the threaded section, according to the diameter of the hole,the wedging means 48 can be positioned initially and assembled at anydesired point on the threaded section prior to insertion of the hole toinsure frictional contact with the hole which will cause its rearwardtravel as the screw anchor is tightened in the hole.

In another modified form of invention shown in FIGS. 5 and 6, themodified form of expansion bolt 50 once again takes the form of a screwanchor having a shank portion 52 which terminates at its leading end ina threaded section 54 and has an enlarged head 55 at its external ortrailing end, together with a separate washer 55'. Again the threadedsection 54 forms a part of a wedging assembly, each threaded portion 54being of generally truncated, V-shaped cross-section separated byrelatively broad annular grooves 56 for placement of resilient wirewedging means 58 therein.

It will be noted that each annular groove includes a radially extendingshoulder portion 60, an axially extending surface portion 62 which isseparated from the shoulder surface 60 by a notch 63, and a forwardlydivergent bearing surface portion 64 which forms one side of thethreaded portion 54. The opposite side of the threaded portions 54 isdefined by the shoulder surface 60 and the external surface of eachthreaded portion is defined by a relatively flat outer peripheralsurface 66.

The resilient wire wedging means 58 is again defined by a spring wirepreferably having a number of turns less than the number of threads 54and has a square cross-section, as best seen from FIG. 6, which is of athickness when normally disposed against the axial surface portion 62 ofthe groove to be extended slightly beyond the outer peripheral outlineof the bolt.

When the bolt is threaded into a drilled hole of a diametercorresponding substantially to that of the bolt, frictional engagementof the wedging means 58 with the wall of the hole will cause the onecorner 68 of the wire to be tipped rearwardly into the notched portion63 of the annular groove and to tip the opposite diagonal corner 70upwardly away from the grooves. Accordingly, the effective thickness ofthe wire will be increased as the wire is tipped or cocked outwardly andwedged or anchored more firmly into the wall of the hole. If desired,the threaded section 54 of the bolt may be tapered in the same manner asdescribed with reference to FIGS. 3 and 4 so that as the bolt isthreaded into the drilled hole the wire will be caused to travelrearwardly along the threaded sections and to expand bothcircumferentially and by tipping into the shallow notch of the annulargroove to increase the degree of anchored engagement with the hole.

Still another modified form of the present invention is shown in FIG. 7wherein an expansion bolt 72 has a bolt shank 74, threaded section 75 atits leading end and a head 76 at its trailing or external end with aseparate washer element 77. The threaded section 75 is made up ofhelical threads 78 separated by annular grooves 80. The configuration ofthe threading and annular grooves is modified in this form to someextent to accommodate a resilient wire wedging means 82 of a length toextend substantially the full length of the threaded section, and anaxially directed, open slot 84 is provided in the external surface ofthe shank portion 74 in communication with the first annular groove 80of the threaded section to receive an axially extending terminal endportion 84 of the wedging means 82.

Considering the specific configuration of the annular grooves 80, itwill be noted in this form that each includes a shoulder surface portion85, an axial surface portion 86 forming a deeper portion of the groovewhich merges into a forwardly divergent bearing surface portion 88 alongone side of each of the threaded portions 78.

The resilient wire wedging means 82 is of circular cross-section and ofa diameter corresponding to, or slightly greater than, the depth of thegroove so that the spring wire will project outwardly from the groovewhen disposed in the deeper portion to a slight extent beyond theperipheral outline of the threaded portion 78.

As the bolt is threaded into a drilled hole corresponding substantiallyto the diameter of the bolt, and in a direction counter to the spiraldirection of the extension of the wire within the groove, the wire willbe caused to expand in a circumferential direction away from the deeperportion of the groove, since its terminal end 84 will lock the wireagainst any travel along the surface of the annular groove. Alternately,in this form, a separate nut may be positioned on the external end inplace of the headed portion 76 so that as the nut is tightened the wire82 will prevent turning of the bolt in the hole as it is inserted butwill be free to slide forwardly along the surface of the groove until itis expanded into anchored engagement much in the manner of the form ofFIGS. 1 and 2.

Although the present invention has been described with a certain degreeof particularity, it is understood that the present disclosure has beenmade by way of example and that changes in details of structure may bemade without departing from the spirit thereof.

What is claimed is:
 1. A masonry expansion bolt for attachment within abolt hole comprising:a generally cylindrical shank portion adapted forinsertion in a bolt hole and having a diameter equal to or slightly lessthan the bolt hole; a wedging section extending at least along a portionof said shank including a plurality of annular ridge portions spacedapart along the length of the wedging section and separated by forwardlydivergent annular grooves, the annular grooves each provided with afirst relatively deep, wire-receiving surface portion divergingforwardly at a low gradual angle and a second bearing surface portion atthe leading end of each groove diverging forwardly at a steeper anglethan the first portion and merging into a ridge portion each ridgeportion having an annular shoulder portion which merges into the nextfirst wire-receiving surface portion; and resilient wire wedging meansnormally disposed in the deeper portions of each of the grooves whensaid shank is inserted into a bolt hole, said spring wire means eachbeing selectively expansible in an outward radial direction by riding upthe first and second diverging surface portions into wedging engagementwith the wall of the hole after the shank is fully inserted into thebolt hole and urged in the direction of withdrawal from the bolt hole.2. A masonry expansion bolt according to claim 1, said resilient wirewedging means each being a ring having a split end portion and aflattened surface portion diametrically opposite to the split endportion to permit ease of flexing in expanding said ring over said shankand returning said ring to a retracted position spaced somewhatoutwardly of said deeper portion with the effective circumference ofsaid ring being slightly greater than the circumference of said shank,and said ring being slidable forwardly along said forwardly divergentbearing surfaces when the shank is urged in the direction of withdrawalfrom the hole so as to be expanded into wedging engagement with the wallof the hole.